Methods of preparing 21-fluoro-16,17-alkylidenedioxy-3,20-diketo-pregnanes

ABSTRACT

A fluorination method for preparing 21-fluoro-pregnanes and also methods of preparing 9 Alpha ,11 Beta -dichloro-6 Alpha ,21difluoro-16 Alpha ,17 Alpha -alkylidenedioxy-pregna-1,4-diene3,20-dione and 9 Alpha ,11 Beta -dichloro-6 Alpha ,21-difluoro16 Alpha ,17 Alpha -alkylidenedioxy-pregn-4-ene-3,20-dione derivatives from the corresponding 21-acyloxy-6 Alpha -fluoro-16 Alpha ,17 Alpha -alkylidenedioxy-3,20-diketo-pregnane derivatives. The fluorination process comprises (1) displacement of the corresponding 21-mesyloxy, or 21-tosyloxy, pregnane derivative with bromide ion to yield the corresponding 21-bromo pregnane derivative, and (2) displacement with fluoride ion to effect replacement of the 21-bromo thereby yielding the corresponding 21-fluoro pregnane derivative. A salient feature is the use of a sulfone solvent in the fluoride displacement step, thereby affording improved yields and purer products. The process of preparing 9 Alpha ,11 Beta -dichloro-6 Alpha ,21-difluoro-16 Alpha ,17 Alpha -alkylidenedioxy-3,20-keto-pregna-1,4-diene or pregn-4-ene derivatives comprises treating the corresponding 21bromo-6 Alpha -fluoro-16 Alpha ,17 Alpha -alkylidenedioxy-3,20dione-pregnane derivatives according to the aforementioned displacement process in combination with a subsequent 9 Alpha , 11 Beta -chlorination process. The aforementioned processes are characterized by high yields and high purity products.

United States Patent 1 1' Alvarex [451 Apr. 17, 1973 .[75] Inventor: Francisco S.-Alvarex, Sunnyvale,

Calif.

[73 1 Assignee: Syntex Corporation, Panama, Pana- [22] Filed: May 26, 1971 [21] Appl. No: 147,218

52 US. Cl. ..260/239.55 D

[51] Int. Cl ..C07c 173/00 I [58] Field of Search ..260/239.55 D

[56] I References Cited UNITED STATES PATENTS 3.226383 12/1965 Ringold et a1. .260/23955 D Primary E.raminef-Elbert L. Roberts AttorneyEvely'n K. Merker, Gerard A. Blaufarb and Lawrence S. Squires ABSTRACT A fluorination method for preparing 2l-fluoro pregnanes and also methods of preparing 9a,ll;6-'

dichloro-6a,2 l-difluoro- 16a, 1 7oz-alkylidenedioxypregna-l ,4-diene-3,20-dione and 9a, 1 l B-dichloro-6a ,21-difluoro-16a,1 7a-alky1idenedioxy-pregn-4-ene- 3,20-dione derivatives from the corresponding 21- acyloxy-6a-fluoro-16a, 1 7a-alkylidenedioxy- 3 ,20- diketo-pregnanederivatives. The fluorination process comprises (1) displacement of the corresponding 2l mesyloxy, or 2l-tosyloxy, pregnane derivative with bromide ion to yield the corresponding 21-bromo pregnane derivative, and (2) displacement with fluoride ion to effect replacement of the 2l-bromo thereby yielding the corresponding 2l-fluoro pregnane derivative. A salient feature is the use of a sulfone solvent in the fluoride displacement step, thereby affording improved yields and purer products. The process of preparing 911,1 lB-dichloro-6a,21-difluoro-16a,17aalkylidenedioxy-3,20-keto-pregnal ,4-diene or -pregn- 4-ene derivatives comprises treating the corresponding 2 l -bromo-6oz-fluoro- 16a, 1 7a-alkylidenedioxy-3,20- dione-pregnane derivatives according to the aforementioned displacement process in combination with a subsequent 901,1 lB-chlorination process. The aforementioned processes are characterized by high yields and high purity products. 1

23 Claims, No Drawings METHODS OF PREPARING 2l-FLUORO-l6,l7- ALKYLIDENEIJIOXY-S ,ZO-DIKETO-PREGNANES BACKGROUND OF THE INVENTION l. The Invention This invention relates to methods for effecting the introduction of 2l-fluoro groups into pregnane steroids. In a further aspect this invention relates to methods of preparing 9a,l lB-dichloro-6a,2 l -difluoro- 1 6a, 1 7a-alkylidenedioxy-3 ,ZO-diketo-pregna-1,4-diene, and pregn-4-ene derivatives from the corresponding 21- acyloxy-pregnane derivatives. In a still further aspect this invention-relates to the introduction of a bromide at the 2l-position, then replacement of the 21-bromo c is used to introduce the 9aand lIB-chloro groups. I

have now discovered that by conducting the fluorination treatment in two steps via a 21-bromo intermediate, and by conducting the displacement of the 21- bromo with fluoride ion using tetramethylene sulfone as the solvent, that increased yields and higher purity products are obtained.

SUMMARY OF THE INVENTION In summary the fluorination process of my invention comprises treating 21-brom0-6a-flu0ro-20-keto steroids with an alkali metal fluoride salt in the presence of the specific solvent tetramethylene sulfone thereby yielding the corresponding 6rx,2l-difluoro-20-keto steroids.

In summary 2l-alkylor acyl sulfonate --keto steroids can be converted to the corresponding 21-fluoro steroids, according to my invention, by replacement of the 2l-alkyl or acyl sulfonate group with a 2l-bromo group'and then treating the 2l-bromo steroid according to the fluorination process described above.

In summary theprocess of my invention of preparing 9a ,l l B-dichloro-6a,2 l -difluoro-l 601, l 7a-alkylidenedioxy-pregna-l,4-diene (-pregn-4-ene) -3,20- diones or pregna-4 ene-3,20-diones comprises the steps of (1) hydrolysis of a 2l-acyloxy-6a-fluoro- 16a, l7walkylidenedioxypregnal ,4.9(l l)-triene- 3.20-dione or -pregna-4,9(l l)-diene-3.2()-dione start- 'ing material or a 2l-acycloxy-6a-fluoro-ll-B-hy- -droxy-l6 a, l7a-alkylidenedioxy-pregna-l,4-diene- 3.20-dione or-pregn-4-ene-3,ZO-dione to yield the corresponding 2l hydroxy intermediate; (2) alkyl sulfonate or aryl sulfonate etherification of the 21- hydroxy intermediate yielding the corresponding 2l.-alkyl sulfonate or 2l-aryl sulfonate intermediate;

-(3) bromination of the 2l -alkyl or aryl sulfonate intermediate to yield the corresponding 2l-bromo intermediate; (4) fluorination of the2lbromo intermediate to yield the corresponding 2l-fluoro intermediate; and (5) selective chlorination of the 21- fluoro intermediate to yield the corresponding 9a,l 1,8-dichloro6oz,2 l difluoro-16a, l 7a-alky-lidenedioxy-pregnal,4-diene-3,20diene or pregn-4-ene- 3,20-dione derivative.

The invention will be further described hereinbelow.

DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS The fluoride replacement process of my invention has general applicability to the replacement of 21-' bromo groups of 2l-bromo-6a-fluoro-20-keto steroids, with 2l-fluoro groups and is of particular interest with respect to the preparation of the 6a,21-difluoro s teroids of formula C, below. Accordingly, for purposes of simplicity, the process will be described with respect to the preparation of such compounds, though it should be remembered that the process has general applicability. The fluorination process of my invention can be conveniently schematically represented, using partial pregnane steroidal formulas, by the following overall reaction equation:

wherein thedotted 1-2 bond line indicates either a carbon-carbon single bond or a carbon-carbon double bond. g

The b'romination step can be conveniently effected by treating the pregnane starting material (formula A) with an alkali metal bromide salt in the presence of a suitable inert organic solvent. Typically, the treatment is conducted at temperatures inthe range of about from to 1 10 C for aboutfrom 6 to 24 hours using reactant mole ratios in the'range of about from 1 to 10 moles of bromide salt-per mole of pregnane starting materiaLand preferably about from 2 to 3 moles of bromide salt'per mole of pregnane starting material.

However, temperatures, treatment durations and mole ratios both above and below these can also be used. Best results are obtained by conducting the treatment at reflux and preferably under anhydrous conditions. Suitable alkali metal bromide salts which can be used include, for example, lithium bromide, sodium bromide, potassium bromide, and the like. Suitable inert organic solvents which can be used include, for example, acetone, tetramethylene sulfone, dimethyl-sulfoxide, dimethyl acetamide, dimethylformamide, and the like. We have further found that best results are obtained by using lithium bromide with tetramethylene sulfone.

The fluorination step is conducted according to my invention by treating the 21-bromo intermediate (formula B) with a suitable alkali metal fluoride salt in the presence of the solvent tetramethylene sulfone. Typically, the. treatment is conducted at temperatures in the range of about from 100 to 135 C, and preferably about from 125 to 135 C for about from 12 to 48 hours and preferably about from to 24 hours using reactant mole ratios in the range of about from 2 to 10 moles of fluoride salt per mole of pregnane starting material (i.e., formula B) and preferably about from 2 to 3 moles of fluoride salt per mole of pregnane starting material. However, temperatures, treatment durations, and mole ratios both above and below these can also be used. Best results are obtained by conducting the treatment at temperatures in the range of about from 130 to 135 C and preferably the treatment is conducted under anhydrous conditions. Suitable alkali metal fluoride salts which can be used include, for example, potassium fluoride, cesium fluoride, and rubidium fluoride. Best results are obtained with potassium fluoride. A salient feature of this step is the use of tetramethylene sulfone and its selectivity to the alkali metal fluoride salts listed above. I have discovered that by the use of the particular solvent and these alkali metal fluoride salts that yields are greatly enhanced and much purer products are obtained. Typically a tetramethylene sulfone steroid ratio in the range of about from 3 to 10 ml. of .tetramethylene sulfone per gram of steroid is used. Best results are obtained by using a ratio of about 3 ml. of tetramethylene sulfone per gram of steroid.

The process-of my invention of preparing 901,113- dichloro-6a,2l-difluoro-1601,!7a-alkylidenedioxypregna-l,4-diene-3,20-dione derivatives and 911,116- dichloro-6a,2l-difluoro-l 6a,17a-alkylidenedioxypregn-4-ene-3,20-dione derivatives can be veniently represented by the following schematic overall reaction equation:

con-

wherein Ac is acyl having from two to 12 carbon atoms; R is hydrogen or lower alkyls having from one through seven carbon atoms, R and R are independently hydrogen or lower alkyls having from one through seven carbon atoms, or together with the carbon atom to which they are joined form a cycloalkyl group having five through seven ring carbon atoms, and the dotted bond line indicates a single or double bond, and preferably R and R are each methyl and the dotted line'is a double bond.

Starting with the corresponding 2l-acyloxy (typically a 21-acetoxy) starting material of formula I, the Zl-acetylgroup is removed by hydrolysis, step l'of my invention. This can be effected by any suitable hydrolysis procedure and can, for example, be conveniently effected by treating the compound of formula I or la with a suitable alkyl alcohol containing a small amount of potassium carbonate. This treatment is typically conducted at temperatures in the range of about from 0 to 100 C. Suitable alkyl alcohols include, for example, methanol, ethanol, and the like. Also, in place of potassium carbonate, the following reagents could be used, sodium carbonate, and the like. The hydrolysis step is a conventional procedure as thus optimum conditions can be obtained by routine experimentation, or alternatively, other equivalent hydrolysis procedures can be used such as those described in US. Pat. No. 3,409,613 (Example I (A)). The compounds of formula III or Illa are. respectively prepared by treating the corresponding compounds of formula ll or lla with mesyl chloride or tosyl chloride in a suitable inert organic solvent, thereby yielding the corresponding 2l-mesyloxy or 21- tosyloxy derivative Typically, this treatment is conducted at temperatures in the range of about from 0 to 50 C for about from 1 to 12 hours using reactant mole ratios in the range of about from 1 to moles of mesyl chlorideor tosyl chloride per mole of pregnane starting materialof formula II or lla. However, temperatures, treatment durations and mole ratios both above and below these ranges can also be used. Suitable inert organic solvents which can be used include, for example, pyridine, collidine, and the like. Also, inplace of mesyl chloride or tosyl chloride, other lower alkyl sulfonyl chlorides or lower aryl sulfonyl chlorides could be used, however, best results are obtained by using either mesyl chloride or tosyl chloride, and preferably using mesyl chloride.

Steps 3 and 4 correspond to the bromide replacement and fluoride replacement steps, respectively, of my invention, and are conducted in the same manner, as described hereinabove.

Step 5, the chlorination step, can be performed according to any suitable chlorination procedure. The compounds of formula V can, for example, be conveniently chlorinated to the corresponding compounds of formula Vl via treatment with gaseous chlorine in a suitable inert organic solvent. Preferably this treatment is conducted under anhydrous conditions. Also, as the mentation. The compounds of formula Va can be conveniently chlorinated to afford the compounds of for mula Vl, according to the chlorination process 31, 1970, via treatment with thionyl chloride and chlorine. This treatment is typically conducted in a liquid reaction media and in the presence of a tertiary chlorination step is a conventional procedure, optimum 50 conditions can be obtained by nominal routine experidescribed in my Belgium Patent 744,618, issued Mar. 65

amine, at temperatures in the range of about -10 to 30 C for about from i to minutes. Suitable inert liquid reaction media include, for example, dimethylsulfoxide, acetic acid, methylene chloride, tetrahydrofuran, and the like. Typically about from 0.9 to 5 moles of thionyl chloride and also about from 0.9 to 5 moles of chlorine, and about from 1 to 10 moles of tertiary amine per mole of compound of formula Va are used. However, temperatures, treatment times, and mole ratios both above and below these can also be used.

Preferably, each of the respective intermediate products formed by the above reaction steps is isolated prior to its use as the starting materials for the next succeeding step. Separation and isolation of the intermediates and products can be effected by any suitable separation or purification procedure such as, for example, extraction, filtration, evaporation, crystallization, and thin-layer chromatography. Specific illustrations of typical separation and isolation procedures can be had by reference to the examples described hereinbelow.

However, other equivalent separation or isolation procedures could, of course, also be used.

As described hereinabove and below, the following terms have the following meanings". The term lower alkyl refers to both straight chain and branched chain alkyl groups having from one through seven carbon atoms. The term lower aryl refers toaryl groups having one or two lower alkyl substituents such as, for example, p-toluene or o-methyl-p-toluene. The term acyl refers to acyl groups having'from two through,l2 carbon atoms. Typical acyl groups include, for example, acetyl, propionyl, butyryl, valeryl, isovaleryl, hexanoyl, heptanoyl, octanoyl, nonanoyl, undecanoyl, lauroyl, benzoyl, p-methoxy-benzoyl, p-nitrobenzoyl, phenylacetyl, phenylpropionyl, 0-, m-, p-methylbenzoyl, B- cyclopentylpropionyl, dihydrocinnanyl and the like.

A further understanding of the invention can be obtained from the following illustrative non lirniting examples.

EXAMPLE 1 This example illustrates hydrolysis of the acetoxy group at the 2l-position to yield the corresponding 2lhydroxy-pregnane. In this example 157 grams of 21- acetoxy-Ga-fluoro- 1 601,1 7a-isopropylidenedioxypregna-1,4,9( l 1)-triene-3,20-dioneis suspended in 3,000 ml. of anhydrous methanol. Six grams of finely divided potassium carbonate is then added under a nitrogen atmosphere and the mixture is stirred under a nitrogen atmosphere, at room temperature (i.e., about 20 C), for 3 hours. The mixture is then neutralized by the addition of 15 ml. of glacial acetic acid and then concentrated undervacuum to a. small volume (i.e., about 300 ml.) and then diluted by the slow addition of 5 liters of water. The resulting crystalline precipitate is collected by filtration and dried under vacuum at to C, affording tic-fluoro-Q.lahydroxydfimi7ailsopropylidenedioxy-pregna-l ,4,9( l l )-triene-3.20-

ione.

By following the same procedure as above but using the corresponding pregnanc derivative as a starting material, the following are respectively prepared:

6a-fluoro-2 l -hydroxy- 1 601,1 7a-methylidenedioxypregna-l ,4,9-(1 i )-trierus-El,ZO-dione;

lidenedioxy-pregna-l,4,9-(1 1 )-triene-3,20-dione;

- 60z-fluoro-16a,l7a-cyclohexylidenedioxy-Zlhydroxy-pregna-l,4,9-(1 1 )-triene-3,20-dione;

, 2 l-acetxy-6a-fluoro-16a, l 7a-methylidenedioxypregna-4,9(l l )-diene-3,20-dione;

6a-fluoro-2l-hydroxy-16a,17a-isopropylidenedioxy-pregna-4,9(1 1 )-diene-3,20-dione;

6a-fluoro-2 1 -hydroxy- 1 6a, 1 7a-cyclopentylidenedioxy-pregna-4,9(1 1 )-diene-3,20-dione;

hydroxy-pregna-4,9(1 1)-diene-3,20-dione;

6a-fluoro-9B,21 -dihydroxy- 1 6a, 1 7a-methylidenedioxy-pregna- 1 ,4diene-3 ,20 -dione;

, 6a-fluoro-9,B,21 -dihydroxy-16a,17a-isopropylidenedioxy-pregna-l ,4-diene-3 ,ZO-dione;

6a-fluoro-9B,2l-dihydroxy-16a,l7a-cyclopentylidenedioxy-pregna-l ,4-diene-3,20-dione;

6a'-fluoro-160:,17a-cyclohexylidenedioxy-9B,21- dihydroxy-pregna- 1 ,4-diene-3,20-dione;

6a-fluoro-9B,21-dihydroxy-16a,17a-methylidenedioxy-pregn-4-ene-3,20-dione;

60z-fluoro-9B,2 l-dihydroxy-l 601,1 7a-isopropylidenedioxy-pregn-4-ene-3,20-dione;

6a-fluoro-9/3,2 l-dihydroxy-l 601,1 70z-cyc1opentylidenedioxy-pregn-4-ene-3,20-dione; and

6a-fluoro-1601,17a-cyclohexylidenedioxy-9B,21- dihydroxy-pregn-4-ene-3,20-dione.

EXAMPLE 2 This example illustrates mesylation of the 21-hydroxy group to yield the corresponding 21-mesyloxypregnanes. In this example 136 g. of 6a-fluoro-21- hydroxy-l 601,1 7a-isopropyl-idenedioxy-pregna- 1,4,9(l1)-triene-3,20-dione is dissolved in 1,360 ml. of anhydrous pyridine and the resulting mixture then cooled to about 0 to C. 95 Ml. of mesyl chloride is then slowly added and the resulting mixture stirred under anhydrous conditions at 0 to 5 C for 2 hours. The reaction mixture is then diluted slowly with 10 l. of water, resulting in a crystalline precipitate which is then collected by filtration and dried at 40 to 50 C,

under 'vacuum, affording 6a-fluoro-2l-mesyloxy- 16a,17 rx1,4,9(1 1)-triene- 3,20-dione.

, ,By following the same procedure as above but using the corresponding pregnane derivative as a starting material, the following are respectively prepared:

6a-fluoro-l 6a,17a-methylidenedioxy-2 1 -mesyloxypregna-1,4,9(1 1)-triene'-3,20-dione;

6a-fluoro-2l-mesyloxy-160:,1 7a-cyclopentylidenedioxy-pregna-l ,4,9( 1 1 )-triene-3,20-dione; 6a-fluoro-16a,1 7a-cyclohexylidenedioxy-2 1- mesyloxy-pregna-l ,4,9( 1 1 )-triene-3,20-dione;

21-acetoxy-6a-fluoro-l6a,17a-methylidenedioxypregna-4,9( 1 1 )-diene -3,20-dione;

6a-fluoro-l611,170z-isopropylidenedioxy-2 1- mesyloxy-pregna-4,9( l l )-diene-3,20-dione;

6a-fluoro-2l-mesyloxy-l6a,17a-cyclopentylidenedioxy-pregna-4,9(l 1 )-diene-3,20-dione;

fia-fluoro- 1 601,1 7oz-cyclohexylidenedioxy-2 1 mesyloxy-pregna-4,9( 1 l )-diene-3,20-dione;

6a-fluoro-9B,21-dihydroxy-mesyloxy-l 6a, 1 7amethylidene-dioxy-pregna-1,4-diene-3 ,20-dione;

6a-fluoro-9B-hydroxy-1601,]7a-isopropylidenedioxy-2-1-mesyloxy-pregna-1,4-diene-3,20-dione;

6a-fluoro-9/3-hydroxy-2l-mesyloxy-l 601,1 7a- EXAMPLE 3 This example illustrates bromination of the 21- mesyloxy group to the corresponding 2l-bromo pregnanes. In this example 156 grams of 6a-fluoro-21- hydroxy-l6a,17a-isopropylidenedioxy-pregn'a- 1,4,9( 1 1)-triene-3,20-dione-21-mesylate is dissolved in 1,000 ml. of acetone containing g. of lithium bromide. The mixture is stirred and refluxed under anhydrous conditions for 8 hours. The reaction mixture is' then diluted by the slow addition of 600 ml. of water and then evaporated under reduced pressure to remove the acetone. The concentrated mixture is then further diluted by the addition of 7 liters of water resulting in the formation of a precipitate which is then collected by filtration and dried at 40 to 50 C, under vacuum, affording 21-bromo-6a-fluoro-16a,17a-isopropylidenedioxy-pregna-l,4,9(11) triene-3,20-dione.

By following the same procedure as above but using the corresponding pregnane derivative as a starting material, the following compounds are respectively prepared:

2 1 -bromo-6a-fluoro-l 611,1 7a-methylidenedioxypregna-1,4,9(1l)-triene3,20-dione;

21-bromo-6a-fluoro-1601,17a-cyclopentylidenedioxy-pregna-l,4,9(11)-triene-3,20-dione;

21-bromo-6a-fluoro-16a,17a-cyclohexylidenedioxy pregna-1,4,9( l l )triene-3,20dione; v

21-bromo-6a-fluoro-16a,l7a-methylidenedioxypregn a-4,9( 1 1 )-diene-3,20-dio'ne; U 21-bromo-6a-fluoro-l601,17a-isopropyliden edioxypregna-4, 9(11)-diene-3,20-dione; v I 21-bromo-6a-fluoro-l601,17a-cyclopentylidenedioxy-pregna-4,9(1 l )-dien e-3,20-dione;

2 1-bromo-6a-fluoro-16a,l 7a-cyclohexylidenedioxypregna-4,9(l1)-diene-3,20-dione;

21-bromo-6a-fluoro-9B-hydroxy-16a,17a-methylidenedioxy-pregna-l ,'4-diene-3 ,20-dione;

2 l-bromo-6a-fluoro9,8-hydroxy-l 6a,1 7a-isopropylidene-dioxy-pregna-l ,4-dien'e-3 ,20-dione;

2l-6a-fluoro-16a,17a-cyclopentylidenedioxy-9B- hydroxy-pregna- 1 ,4-diene-3,20-dione;

2 l-bromo-6a-fluoro-l601,17a-cyclohexylidenedioxy- 9,8-hydroxy-pregna-l,4-diene-3,20-dione;

21-bromo-6a-fluoro-9B-hydroxy-l6a,17a-methylidenedioxy-pregn-4-ene-3,20-dione;

2 1-bromo-6a-fluoro-9B-hydroxy-16a,17a-isopropylidene-dioxy-pregn-4-ene-3,20-dione;

2l-bromo-l611,17a-cyclopentylidenedioxy-6afluoro-9/3-hydroxy-pregn-4-ene-3,20-dione; and

2l-bromo-l601,17a-cyc1ohexylidenedioxy-6a-fluoro- 9B-hydr0xy-pregn-4-ene-3,20-dione.

EXAMPLE 4 This example illustrates fluorination replacement of the 2l-bromo group to yield the corresponding 21- fluoro-pregnanes. In this example, 50 grams of anhydrous potassium fluoride is added to 45 g. of 21- bromo-6a-fluoro-l611,1711 -isopropylidenedioxypregna-l,4,9( l l )-triene-3,20-dione in 150 ml. of tetramethylene sulfone with constant stirring. The mixture is heated to 110 C and maintained at this temperature for 14 hours with constant stirring. The temperature of the reaction mixture is then raised to 140 C and maintained'at this temperature for 9 hours and then lowered to a temperature of about from 110 to 115 C and maintained at this temperature for 12 hours. The reaction mixture is then cooled and poured into 3 liters of cold water, resulting in the formation of a crude 611,2l-difluoro-l6a,l701-methylidenedioxypregnal,4,9( 1 l )-triene-3,20dione precipitate which is collected by filtration anddried under a vacuum mat at60 C. The resulting crude residue is dissolved in 250 ml. of methylene chloride, then diluted by the slow addition of 850 ml. of hexane, with constant Stirring, and then filtered. The resultingproduct-rich filtrate is collected. The filter cake is redissolved in 200 ml. of

methylene dichloride and reprecipitated with 850 ml. of hexane and then filtered. This procedure is repeated two-more times with the filtrate being retained ineach case. All of the filtrates are then combined. Powdered activated charcoal is added to the combined filtrates resulting in -a suspension which is then filtered over Celite to remove the charcoal and adsorbed impurities. The resulting filtrate is evaporated to dryness under vacuum resulting in a crystalline product which is further purified by recrystallization using a methylene chloride-ethyl acetate solvent. A small quantity of additional 611,2 1 -difluoro-l 6a,l 711-isopropylidenedioxypregna-l",4,9( l1)-triene-3,20-dione product is obtained by washing the recovered activated charcoal with methylene chloride. The washings are combined and then evaporated to dryness. The. resulting residue is dissolved in a 4:1, by volume, mixture of hexane and methylene chloride, and then filteredthrough a column of neutral alumina. The column is washed twice with 100ml. portions of the same solvent mixture. The

washings are combined with the initial eluates and then evaporated to dryness under reduced pressure. The

611,2 1 -difluoro-9B-hydroxyl 601, l 711isopropylidened EXAMPLE 5 This example illustrates chlorination at the 911,1 lB- position of 611,2l-difluoro-9( l l )-ene pregnanes to afford the corresponding 911,l lB-dichloro-pregnane compounds. In this example l7.7 g. of 611,2l-difluorol 611,1711-isopropylidenedioxy-pregna-l ,4,9( l l )-triene- 3,20-dione is dissolved in a mixture of 265 ml. of anhydrous chloroform and 35 ml. of pyridine. The mixture is then treated with a slow stream of dry chlorine under anhydrous conditions with constant stirring, until analysis by thin-layer chromatography of respective samples taken at sequential time intervals reveals the completion of the reaction. The reaction mixture is then evaporated under vacuum at about 35-409 C to a volume of ml. Ml. of ethyl acetate are added to the mixture and the mixture again evaporated under,

vacuum at35-40 C to remove the chloroform and most of the pyridine The mixture is then-cooled to room temperature (i.e., about 20 C) affording a crude precipitate of 911,1 lB-dichlo ro-611,2 l -difluoro-l 6 11,1711-isopropylidenedioxy-pregna-l ,4-diene -3,20-

dione which is then recovered by filtration, dried and further purified by recrystallization, first using a methylene chloride-ethyl acetate solvent and 1 then.

using a pure methylene chloride solvent. 1

By following the same procedure as above but using 1 the corresponding pregnane derivative as a starting material, the following are respective prepared;

911,1 lB-dichloro-611,2l -difluoro l 611,1.711-methylidenedioxy-pregna-l ,4-diene-3,20-dione;

911,1 lB-dichloro-6o1,2 l -difluoro -l 611,1 7a-cyclopenf EXAMPLE 6 This example illustrates methods of preparing 911,1lB-dichloro-611,2l-difluoro-p:regnanes from the corresponding 601,21-difluoro-l lB-hydroxy pregnanes. In this example l molar equivalent of thionyl chloride and 1 molar equivalent of chlorine are dispersed in 1 liter of chloroform at room temperature (about 20 C).

isopropylidenedioxy-pregna-l ,4-diene-3 ,20-dione is dispersed in 100 ml. of chloroform containing 10 ml. of triethyl amine at room temperature. Ten milliliters of the thionyl chloride, chlorine, chloroform mixture, prepared above, is then added dropwise to the resulting pregnane, chloroform, triethyl amine mixture, with constant stirring, at room temperature. The resulting reaction mixture is cooled to C and maintained at this temperature for 1 hour with constant stirring. The mixture is then washed with dilute hydrochloric acid and then repeatedly washed with water to neutrality. The mixture is then dried over a sodium sulfate and evaporated affording a residue of 9a,11B-dichloro- 601,21-difluoro-l6a,l7a-isopropylidenedioxy-pregnal,4-diene-3,20-dione which is then further purified by recrystallization from acetone/hexane.

By following the same procedure as above but using the corresponding 611,2 1 -difluoro-l lB-hydroxy' pregnane starting materials, the following compounds are respectively prepared:

9a,l lB-dichloro-6a,2l-difluoro-l601,17a-methylidenedioxy-pregnal ,4-diene-3,20-dione;

9a,l lB-dichloro-6a,2l-difluoro-l 611,1 7a-cyclopentylidene-dioxy-pregna-l ,4-diene-3 ,ZO-dione;

9a,l ln-dichloro-la,l7a-cyclohexylidenedioxy- 6a,2l-difluoro-pregna-l,4-diene,-3,20-dione; I

9a,1 1B-dichloro-6a,2l-difluoro-l 601,1 7a-methylidene-dioxy-pregn-4-ene-3,20-dione;

9a,] lfl-dichloro-6a,2 l -difluorol 601, l 7a-isopropylidene-dioxy-pregn-4-ene-3,20-dione;

9a,l lB-dichloro-l6a, l 7a-cyclopentylidenedioxy- 6a,2l -difluoro-pregn-4-ene-3,20-dione; and

9a,l lB-dichloro-l6a,17a-cyclohexylidenedioxy- 6a,21-difluoro-pregn-4-ene-3,20-dione.

Obviously many modifications and variations of the invention, described hereinabove and in the appended claims, can be made without departing from the essence and scope thereof.

What is claimed is:

1. A method of preparing 6a,2l-difluoro-20-ketopregnane steroid which comprises treating the corresponding 2 l -bromo-6a-fluoro-20-keto pregnane steroid selected from the group having the formulas:

. HzC-Br Yfi ii Y 3, wherein R and R are independently selected from the group consisting of hydrogen and lower alkyls having from one through seven carbon atoms or IIIa together with the carbon atom to which they are joined form a cycloalkyl group having from five through seven ring carbon atoms, and the dotted line means that the bond joining the C and C carbon atoms can be either a single or double bond;

with an alkali metal fluoride salt selected from the group consisting of potassium fluoride, cesium fluoride, rubidium fluoride, under reactive conditions, in tetramethylene sulfone.

2. The process of claim 1 wherein said treatment is conducted at temperatures in the range of about from 130 to 135C.

3. The process of claim 1 wherein a volume/weight ratio of tetramethylene sulfone to steroid in the range of about from 3 to ml. of tetramethylene sulfone per gram of said steroid is used.

4. The process of claim 1 wherein a mole ratio of alkali metal fluoride salt to moles of 2l-bromo-6afluoro--keto-pregnane steroid, in the range of about from 2 to 10 is used.

5. The process of claim 1 wherein said alkali metal fluoride is potassium fluoride.

6. The process of claim 1 wherein R and R are each methyl and the bond joining the C, and C atoms is a double bond.

7. The process of claim 3 wherein said treatment is conducted at temperatures in the range of about from 100 to 135 C and a mole ratio of alkali metal fluoride salt to moles of 2l-bromo-6a-fluorosteroid in the range of about from 2 to 10 is used and wherein said alkali metal fluoride salt is potassium fluoride.

8. The process of claim 1 wherein said treatment is conducted at temperatures in the range of about from 100 to 135 C and a mole ratio of alkali metal fluoride salt to moles of 2l-bromo-6a-fluorosteroid in the range of about from 2 to 10 is used and wherein said alkali metal fluoride salt is potassium fluoride.

9. The process of claim 7 wherein said treatment is conducted at temperatures in the range of about from lto lC. i

10. The process of claim 8 wherein said treatment is conducted'at temperatures in the range of about from l30to 135C. 7

11. A method of preparing 6a,21-difluoro pregnane steroids which comprises the steps of:

a. treating a 60a-fluoro steroid selected from the group having the formulas;

LII

Ill

Illa

wherein R" is mesyloxy or tosyloxy, and R and R are independently selected from the group consisting of hydrogen and lower alkyls having from one through seven carbon atoms or together with the carbon atom to which they are joined form a cycloalkyl group having from five through seven ring carbon atoms, and the dotted line means that the bond joining the C and C carbon atoms can be either a single or double bond, with an alkali metal bromide salt, under reactive conditions thereby forming the corresponding 2l-bromo derivative; and

b. treating the 2l-bromo derivative product of step (a) with an alkali metal fluoride salt selected from the group consisting of potassium fluoride, cesium fluoride and rubidium fluoride under reactive conditions in tetramethylene sulfone, thereby forming the corresponding 6a,2l-difluoro pregnane steroid.

12. The process of claim 11, wherein R and R are each methyl and the bond joining the C, and C carbon atom is a double bond.

13. Theprocess ofclaim 11 wherein step (b) is conducted using a volume/weight ratio of tetramethylene sulfone to steroid in the range of about from 3 to ml. of tetramethylene sulfone per gram of steroid.

14. The process of claim 13 wherein step (b) is conducted using a mole ratio of alkali metal fluoride salt to moles of 2l-bromo-6a-fluoro steroid, in the range of about from 2 to 10 is used.

15. The process of claim 14 wherein said alkali metal fluoride salt is potassium fluoride.

16. The process of claim 15 wherein step (b) is con-' wherein R, R and the dotted bond line are as defined in claim 14, wherein said oa-fluoro steroid starting material has the formula:

wherein R, R and the dotted bond line are as defined in claim 14, wherein said 6d-fluoro pregnane steroid starting material has the formula:

me u" wherein RR, R and the dotted bone line are as defined in claim 14, and wherein said corresponding 6a,2l-difluoro steroid of step (b) is treated with thionyl chloride and chlorine, under reactive conditions, thereby forming the corresponding compound of formula VI.

23. The method of claim 22, wherein R and R are each methyl and the bond line joining the C and C carbon atoms is a double bond.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION patent 3, 728, 335 Dated April 17, 1973 fi flg Francisco S. Alvarez (Page 1) It is certified that error appears in the above-identified patent and that said Letters Patentare hereby corrected as shown below:

I Column 1, line 59, "2l-acycloxy" should read 2lacylox;

Column 1, line 59, "llB-" should read 116- Column 2, line 5, "3,20-diene" should read 3,20-dione Column 2,

lines 50-55, that portion of the right hand formula reading:

should read I Column 3, lines 60-65, that portion of formula (Ia) reading:

should read 1 Ill Column 4, lines 60-65, that portion of formula (VI) reading:

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 35 I Dated April 17, 1973 Inventofls) Francisco S. Alvarez (Paqe 2) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 7, line 34, "16a,l7cx-isopropyl-idenedioxy-" should read 16d,l7oc-isopropylidenedioxy- Column 7, line 44,

"l6oc,l7ocl,4,9(ll)triene-" should read l6oc,l7ocisopropyli denedioxy-pregnal,4, 9 (ll) triene- Column 10, line 1, I "16d,l7ocisopropylidened" should read l6oz,l7ocisopropyli dene- Column 10, line 2, "ioxypregna-" should read dioxy-pregna- Column 10, line 3, "6oc-difluoro" should read 6a,2l-difluoro- Column 10, line 5, "160:,17-60- oyolohexylidenedioxy" should read l6oc,l7oc-cyclohexylidene dioxy' Column 10, line 8, "pregny4ene" should read pregnl-ene- Column 11, line 26, "90,lln-dichloroshould read 9a,llBdichloro-- Column 12, line 47, "60oc-fluoro" should read 6oc-fluoro Column 12, lines 49-55, that portion of formula III reading:

should read Column 12, lines 60-65, that portion of formula IIIa' reading:

should read I UI YITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 1 81 imnPlll-H1- 92i.

Inventor) Francisco S. Alvarez (Page 3) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 13, line 59, "claim 14" should read claim 11 Column 14, lines 1-7, that portion of formula III reading:

l ---O R l 2 should read Column 14, line 13, "claim 14" should read claim ll Column 14, lines "23-33, that portion of formula (VI) reading:

E H CF =0 should R read Cl Column 14, line 36, "claim 14" should read claim 11 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3, 728,335 Dated April 17, 1973 Inventor(s) Francisco S. Alvarez (Page 4) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 14, lines 39-45, that portion of formula III reading:

H C-R should C=O 1 read OH R Column 14, line 52, "claim 14" should read claim 11 Signed and sealed this 17th day of September 197 (SEAL) Attest:

McCOY M. GIBSON JR. (3. MARSHALL DANN Attesting Officer Commissioner of Patents 

2. The process of claim 1 wherein said treatment is conducted at temperatures in the range of about from 130* to 135* C.
 3. The process of claim 1 wherein a volume/weight ratio of tetramethylene sulfone to steroid in the range of about from 3 to 10 ml. of tetramethylene sulfone per gram of said steroid is used.
 4. The process of claim 1 wherein a mole ratio of alkali metal fluoride salt to moles of 21-bromo-6 Alpha -fluoro-20-keto-pregnane steroid, in the range of about from 2 to 10 is used.
 5. The process of claim 1 wherein said alkali metal fluoride is potassium fluoride.
 6. The process of claim 1 wherein R1 and R2 are each methyl and the bond joining the C1 and C2 atoms is a double bond.
 7. The process of claim 3 wherein said treatment is conducted at temperatures in the range of about from 100* to 135* C and a mole ratio of alkali metal fluoride salt to moles of 21-bromo-6 Alpha -fluoro- steroid in the range of about from 2 to 10 is used and wherein said alkali metal fluoride salt is potassium fluoride.
 8. The process of claim 1 wherein said treatment is conducted at temperatures in the range of about from 100* to 135* C and a mole ratio of alkali metal fluoride salt to moles of 21-bromo-6 Alpha -fluoro- steroid in the range of about from 2 to 10 is used and wherein said alkali metal fluoride salt is potassium fluoride.
 9. The process of claim 7 wherein said treatment is conducted at temperatures in the range of about from 130* to 135* C.
 10. The process of claim 8 wherein said treatment is conducted at temperatures in the range of about from 130* to 135* C.
 11. A method of preparing 6 Alpha ,21-difluoro pregnane steroids which comprises the steps of: a. treating a 6 Alpha -fluoro steroid selected from the group having the formulas:
 12. The process of claim 11, wherein R1 and R2 are each methyl and the bond joiNing the C1 and C2 carbon atom is a double bond.
 13. The process of claim 11 wherein step (b) is conducted using a volume/weight ratio of tetramethylene sulfone to steroid in the range of about from 3 to 10 ml. of tetramethylene sulfone per gram of steroid.
 14. The process of claim 13 wherein step (b) is conducted using a mole ratio of alkali metal fluoride salt to moles of 21-bromo-6 Alpha -fluoro steroid, in the range of about from 2 to 10 is used.
 15. The process of claim 14 wherein said alkali metal fluoride salt is potassium fluoride.
 16. The process of claim 15 wherein step (b) is conducted at temperatures in the range of about from 130* to 135* C.
 17. The process of claim 11 wherein step (a) is conducted in the presence of an inert organic solvent.
 18. The process of claim 17 wherein said alkali metal bromide salt is lithium bromide and said inert organic solvent is tetramethylene sulfone.
 19. The process of claim 11 wherein said alkali metal fluoride salt is potassium fluoride.
 20. A method according to claim 11 of preparing 6 Alpha ,21-difluoro pregnane steroid having the formula:
 21. A method according to claim 20 wherein R1 and R2 are each methyl and the bond joining the C1 and C2 carbon atoms is a double bond.
 22. A method according to claim 11 of preparing 6 Alpha ,21-difluoro pregnane steroids having the formula:
 23. The method of claim 22, wherein R1 and R2 are each methyl and the bond line joining the C1 and C2 carbon atoms is a double bond. 